A technique used in semiconductor materials manufacturing is thin film growth in a liquid phase epitaxial (LPE) reactor with a mercury-rich melt. By a process well known in the art, a cadmium zinc telluride substrate is exposed to a solution comprising tellurium, mercury and cadmium. This process requires a system capable of withstanding the high mercury vapor pressures that occur at growth temperatures in the approximate range of 500.degree. C., which are required to maintain the crystal growth solution in a molten form. To contain these pressures, the growth chamber of a conventional reactor is normally built from stainless steel, instead of the quartz growth chambers that can be used for low pressure reactors. These steel designs of conventional reactors provide little or no visibility of the film growth process.
Because it would be desirable to view and monitor the film growth in process, the steel chambers currently available may offer ports to view the film growth operations from the top of the chamber or from a side port using a mirror located at the top of a chamber. However, these techniques do not offer optimal visibility in that the distance from the melt to the viewing device is relatively large and the vertical vapor activity from the melt makes it difficult to see the melt across the vertical distance without interference. A quartz washer may be suspended above the melt to reduce the vertical vapor activity; but the presence of the washer may distort the viewing. Additionally, using a mirror to view the melt is awkward and leads to difficulty and complexity in the design and operation of a high pressure reactor. Finally, little external lighting is provided in current reactors, thereby making viewing of the film growth process difficult.
It has therefore become desirable to devise a reactor to allow for direct observation of film growth operations in a high pressure liquid phase epitaxy reactor. A technique for directly viewing growth operations from the side of the reactor chamber, previously not possible, will be discussed in this disclosure.